Photosynthetic H 2 production by green microalgae requires sustained low O 2 while preserving photosynthetic electron supply to FeFe-hydrogenase. We developed a two-compartment bioreactor in which a hydrophobic PTFE membrane separates a concentrated Chlamydomonas reinhardtii pgr5 culture from an iron-based O 2 absorbent, enabling continuous O 2 removal without direct contact between cells and scavenger. After brief N 2 flushing, dissolved O 2 in the culture rapidly dropped to near zero and remained at microoxic levels for multi-day operation; adding silica-gel desiccant improved absorbent performance in the humid sealed reactor and prolonged low-O 2 maintenance. Under high light (350 μmol photons m −2 s −1 ) at 30 °C, the system supported sustained H 2 production for 12 days, reaching 1350 ± 80 μL H 2 mL −1 under the optimal regime. Dark preincubation before high-light exposure reduced H 2 yield and impaired photosystem II performance. These results identify membrane-assisted O 2 removal and product-gas management as effective process-engineering strategies for prolonged algal H 2 production. • We developed a novel method for sustaining H 2 production in C. reinhardtii pgr5 cells. • Membrane-separated, desiccant-stabilized O 2 absorbent sustains anoxia for12 days. • Sustained liquid-phase anoxia supports prolonged H 2 production for 12 days. • Optimal operation yields 1350 μL H 2 ml −1 over 12 days in pgr5 cultures. • OJIP reveals dark-to-high light transition increases PSII acceptor-side limitation.
Khosravitabar et al. (Thu,) studied this question.